This invention relates to conveyor belt system. More particularly, this invention relates to a bed for supporting a conveyor belt. Still more particularly, this invention relates to a roller bed that is inserted between idlers to support the conveyor with adding as little drag or friction as possible.
It is common to use conveyor belts to move bulk materials from one place to another. For example, power plants transport coal from storage piles into hoppers in a processing area using a series of conveyor belts. One problem with the use of conveyor belts is spillage of material. A second problem with the use of conveyor belts is air pollution from dust. The access material and dust may be volatile and can be ignited by any heat or spark introduced into the environment.
Spillage of material typically occurs at a transfer point where material is passed from one conveyor belt to a second conveyor belt. The transfer usually occurs by dropping the material from the first conveyor belt to the second belt. As the material hits the second conveyor, the material sprays with some material falling over the edge of the second conveyor belt. Vibrations caused by outside sources, such as motors, may shake the conveyor belt and cause material to fall off the edges remote from the transfer point.
Air pollution is caused by induced air flow in a conveyor belt system. A stream of bulk material is formed by the material falling or being projected from the first conveyor belt to the second conveyor belt. The individual particles in the stream of bulk materials impart a frictional drag on the surrounding air. The surrounding air begins to flow in the direction of the material stream and attains a velocity approaching the velocity of the material stream. This is called an induced airflow. At the end of the fall, the bulk material is suddenly stopped and compacted caused by impact of the material stream onto the second conveyor belt. The velocity pressure of the induced air flow is converted to static pressure by the impact of the bulk material. A region of high air pressure is created by the static pressure. Air in the region of high air pressure must flow to a region of lower air pressure. As the air flows from the region of high air pressure to the region of lower air pressure, small particles of the bulk material are suspended in the air. In an open system, the movement of the air is from high pressure to low pressure is evidenced by a dust cloud billowing from a loading point of the second conveyor belt.
It is common to use a housing to enclose the second conveyor belt and prevent the dust from billowing and reduce spillage. A skirting hangs from the bottom edge of the housing and drags against the side of the conveyor belt to completely enclose the area. To maintain contact with the skirting, a support is added underneath the conveyor belt. Typically, the support includes beams that run longitudinally with the conveyor belt along each side of the conveyor belt, or large rolls spaced apart on 12 to 18 inch centers. In the case of static bars, or beams, it is a problem that these supports cause drag on the conveyor belt. This drag causes undue exertion by a motor turning the conveyor belt, wear of the skirting and wear of the belt. The drag may also generate undesired heat which may melt the belt, or beams. Therefore, an improved manner of maintaining contact with the skirting is needed. In the case of large rolls on 12 plus inch centers, the belt will sag between the rolls and allow spillage, and impingement points where material wedges between the belt and the wearliner, at each point where the belt sags between these rolls.